Tea vers. — On the Distribution of New Zealand Birds. 181 



I have already mentioned that the North Island possesses nine species 

 peculiar to itself, of which Orthonyx albicilla is represented in the South 

 Island by Orthonyx ochrocephala. The latter is a very different-looking 

 and somewhat more robust bird than its North Island congener, but not- 

 withstanding this difference in size and the greater differences which the 

 two forms present in external characters, they both have precisely the same 

 habits and notes. The differences between the external characters of the 

 species of Petroica, Turdidce, Apterygida, and Ocydromus peculiar to each 

 of the main islands, though less manifest than in the case of the two species 

 of Orthonyx, is very well marked, but in each of these instances also the 

 habits and notes of the birds are the same. In the case of the Oorvidce, 

 the North Island species is only distinguished from the South Island one 

 by its slightly larger size and by the colour of the wattles, but in this 

 instance also the notes and habits of the birds are identical. It will have 

 been observed by those who have seen them in their natural state, that, 

 with the possible exception of Pogonomis cincta, all the birds of flight 

 peculiar to the North Island, and with the exception of the two species of 

 Nestor, all those peculiar to the South Island, which frequent forest habitats 

 in the respective islands, are birds which never voluntarily rise above the 

 level or move outside the limits of the forests in which they dwell, and the 

 chances are, therefore, very remote that any of them should pass, in numbers 

 at all events, across the waters dividing the two islands. 



The same observations may be applied to a large proportion of the 

 species common and peculiar to the two islands, rendering it remarkakle 

 that so many of them should have retained common characters during the 

 enormous period that must have elapsed since the formation of Cook 

 Straits. 



The non-occurrence of Heteralocha acutirostris in the South Island may 

 excite surprise ; but it must be remembered, in the first place, that this is 

 one of the birds which never voluntarily rises above the level or passes 

 outside of the limits of the forest in which it lives, and in the next, that 

 its range, even in the North Island, is restricted to mountain districts so 

 placed that the only winds of sufficient strength to overcome the efforts of 

 stray birds to return to their own special abode, would prevent their 

 crossing the dividing waters. The restriction in the range of this bird 

 is, however, not so surprising as that which occurs in the cases of Nestor 

 occidentalis and Nestor notabilis in the South Island, seeing that, apparently, 

 the very same natural conditions as those which characterize their respec- 

 tive special habitats, extend over a large portion of both islands. We are 

 but little aware of the circumstances which operate in causing a restriction 

 in the range of any particular species, or which may lead to the local 



